3.1
Principle of Program Execution
You can process your STEP 5 user program in various ways.
Cyclic program execution is most common with programmable
controllers (PLCs). The system program runs through a program loop
(the cycle, refer to Section 3.4) and calls organization block OB 1
cyclically in each loop (refer to Fig. 3-1).
C a l l O B 1
B E
C a l l P B 2 0
B E
P B 2 0
O B 1
U p d a t e i n t e r -
p r o c e s s o r c o m m .
f l a g o u t p u t s
i m a g e o u t p u t s
( P I Q )
U p d a t e p r o c e s s
Tr i g g e r c y c l e t i m e
U p d a t e i n t e r -
p r o c e s s o r c o m m .
f l a g i n p u t s
i m a g e i n p u t s
( P I I )
U p d a t e p r o c e s s
f r o m s t a r t - u p
S y s t e m p r o g r a m
U s e r p r o g r a m
Fig. 3-1
Principle of cyclic program execution
Principle of Program Execution
CPU 948 Programming Guide
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C79000-G8576-C848-04
Summary of Contents for CPU 948
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Page 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
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Page 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Page 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Page 538: ...Contents CPU 948 Programming Guide 13 2 C79000 G8576 C848 04 ...
Page 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...